Both Red Bull and Williams are in action at the Silverstone circuit this week, carrying out tyre testing on behalf of Pirelli.
Aside from the regular pre-season and in-season testing, which is open to all the F1 teams and for their benefit, a separate test programme runs throughout the Formula 1 season.
This is specifically for the benefit of Pirelli to evaluate and test prototype tyre compounds, both dry and wet compounds, with all of the teams given the chance to participate over the course of the year.
Staying on at Silverstone for two days of testing this week, Williams and Red Bull Racing are the two teams carrying out this test for Pirelli.
Each team will run a car for two days on Tuesday and Wednesday, with the car running a previously used car setup which the team are not permitted to change. There can be no new developments put on the car, and the team are instructed which tyre compound to use by Pirelli at any given point of the day.
Pierre Gasly is driving the Red Bull for the first day, with George Russell driving the Williams. Robert Kubica has already been confirmed as driving the FW42 on Wednesday, although Red Bull are yet to confirm who will drive their car for Day 2.
This particular test is specifically for dry tyre compound testing. There are four tests remaining over the remainder of the season, with two taking place at Paul Ricard, one at Suzuka and one at the Autodromo Hermanos Rodriguez in Mexico City.
Straight after #BritishGP, we're back on track at @SilverstoneUK for our #Fit4F1 2020 tyre development test. Current weather conditions: sunny, 18° air.
Here's the line-up for Day 1:@redbullracing – @PierreGASLY @WilliamsRacing – #GR63
— Pirelli Motorsport (@pirellisport) July 16, 2019